Charging device

ABSTRACT

A charging device may include a compressor, a bearing housing, a shaft that is rotatably mounted in the bearing housing, a compressor wheel arranged on the shaft, and a diffuser, which may radially extend from a diffuser inlet on the compressor wheel towards a diffuser outlet on a spiral-shaped compressor housing. The diffuser may be delimited by a diffuser wall and a bearing housing wall. A first section of the bearing housing wall may be oriented originating from the diffuser inlet by an angle ranging from 2° to 30° obliquely to a radial direction, and may bring about a tapering of the diffuser cross section in the radial direction away from the shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. DE 102016 217 446.0, filed on Sep. 13, 2016, the contents of which areincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a charging device with a compressor anda shaft which is rotatably mounted in a bearing housing, with acompressor wheel arranged thereon. In addition, the invention relates toan internal combustion engine with such a charging device.

BACKGROUND

From EP 0 386 743 A2 a generic charging device with a compressor and ashaft that is rotatably mounted in a bearing housing, with a compressorwheel arranged thereon, is known. The known charging device additionallyhas a diffuser, which radially extends from a diffuser inlet on thecompressor wheel to a diffuser outlet on a spiral-shaped compressorhousing. Here, the diffuser itself is tapered with respect to its radiallength by way of which a pressure increase and thus an increasedefficiency are to be achieved.

Disadvantageous with the charging device known from the prior arthowever is that at low circumferential speeds and mass flows, i.e. neara surge limit, the risk of a flow separation and a backflow in thediffuser near a bearing housing wall are increased. In particular at lowcircumferential speeds and mass flows, this leads to a reduction of theefficiency.

SUMMARY

The present invention therefore deals with the problem of stating animproved or at least an alternative embodiment for a charging device ofthe generic type, which is characterized in particular by an increasedefficiency in an operating range near the surge limit.

According to the invention, this problem is solved through the subjectof the independent claims. Advantageous embodiments are subject of thedependent claims.

The present invention is based on the general idea of forming, for thefirst time, a bearing housing wall delimiting a diffuser in thedirection of a bearing housing of a compressor not radially, butobliquely, as a result of which in particular in the operating rangenear the surge limit, i.e. at comparatively low circumferential speedsand mass flows, a flow separation and a back flow in the diffuser nearthe bearing housing wall can be reduced. Because of this, the efficiencycan be substantially increased in particular in this operating range.The charging device according to the invention comprises, in the knownmanner, a compressor and a shaft that is rotatably mounted in a bearinghousing and a compressor wheel arranged thereon. Likewise, the chargingdevice comprises a diffuser which radially extends from a diffuser inleton the compressor wheel towards a diffuser outlet on a spiral-shapedcompressor housing. It is now according to the invention that thediffuser on the one hand is delimited by a diffuser wall and on theother hand by a bearing housing wall and at the same time the bearinghousing wall, in a first section originating from the diffuser inlet, isorientated by an angle α of 2°≦α≦30° obliquely to a radial direction andbecause of this brings about a tapering of the diffuser cross section inradial direction to the outside. Through the reduced flow cross section,an increase of the flow velocity in the diffuser can be achieved andbecause of this an increase of the efficiency with low mass flows. Withthe oblique bearing housing wall, the flow in the diffuser isdecelerated and thus pressure build-up, wherein however the specialadvantage and basic idea of the present invention is that the efficiencyat low mass flows and low circumferential speeds, i.e. in particular ina range near the surge limit can be increased, which can be achievedwith the bearing housing wall that is inclined in its first sectionaccording to the invention. Conventional geometries by contrast have theproblem that in the operating points at low circumferential speeds andmass flows the area enlargement in the diffuser in radial direction andthus the deceleration is too great, which as a consequence results inflow separations. The increase of the efficiency in this case is basedin particular on the fact that through the oblique first section of thebearing housing wall a flow separation and a back flow in the diffuserat low rotational speed and mass flows can be reduced.

With an advantageous further development of the solution according tothe invention, a width a on the diffuser outlet corresponds toapproximately 37.5 to 95% of the width B on the diffuser inlet. By wayof such a cross-sectional tapering an increase of the flow velocity or areduction of the deceleration that otherwise occurs in this range takesplace in the radial profile of the diffuser, as a result of which theefficiency of the charging device according to the invention can also beincreased in lower rotational speed ranges.

With a further advantageous embodiment of the solution according to theinvention, a radially extending second section adjoins the first sectionof the bearing housing wall radially on the outside, which opens into avolute of the compressor housing. The radially extending second sectionin this case is dependent on the angle of the inclination and the widtha on the diffuser outlet.

Practically, a radial length L₂ of the second section corresponds to100% to 250% of the radial length L₁ of the first section, wherein theradial length L₂ is obtained from the outer diameter of the diffuser.

With a further advantageous embodiment of the solution according to theinvention, the first section is formed in one piece with the bearinghousing wall. This offers the great advantage that through a simplechange of the shape of the bearing housing the shape of the diffuser canalso be changed at the same time without assembly steps beingsubsequently required for this. In particular, by changing the castingmould of the bearing housing, a diffuser can be created for example atthe same time. Alternatively to this it is obviously also conceivablethat the first and the second section of the bearing housing wall areformed as a separate insert and are connected to the bearing housingwall. This in turn offers the great advantage that the production of thebearing housing with initially radial bearing housing wall can becontinued and merely optionally equipped with the additional first andsecond section. Because of this, a significantly greater flexibilitywith respect to the production is also conceivable in particular, sincefor example different first sections with wedge surfaces of varyinginclination and second sections of varying thickness can be kept instock and can be individually arranged in otherwise same bearinghousings or on otherwise same bearing housing walls. Because of this, amodular system could also be realised in particular.

Further important features and advantageous of the invention areobtained from the subclaims, from the drawing and from the associatedFIGURE description by way of the drawing.

It is to be understood that the features mentioned above and still to beexplained in the following cannot only be used in the respectivecombination stated but also in other combinations or by themselveswithout leaving the scope of the present invention.

A preferred exemplary embodiment of the invention is shown in thedrawing and is explained in more detail in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The only FIGURE shows a sectional representation through a chargingdevice according to the invention.

DETAILED DESCRIPTION

According to the FIGURE, a charging device 1 according to the invention,which can be designed in particular as exhaust gas turbocharger 2 in amotor vehicle, comprises a compressor 3 and a shaft 5 that is rotatablymounted in a bearing housing 4 with a compressor wheel 6 arrangedthereon. Likewise, the charging device 1 according to the inventioncomprises a diffuser 7, which radially extends from a diffuser inlet 8on the compressor wheel 6 towards a diffuser outlet 9 on a spiral-shapedcompressor housing 10. According to the invention, the diffuser 7 is nowdelimited on the one hand by a diffuser wall 11 and on the other hand bya bearing housing wall 12. According to the invention, the bearinghousing wall 12 is orientated on a first section originating from thediffuser inlet 8 obliquely to a radial direction 14 by an angle αbetween 2 and 30° and brings about a tapering of the diffuser crosssection in radial direction 14 towards the outside. A bearing housingwall which a compressor known from the prior art and designed as usualwould have is drawn with dashed line and marked with the referencenumber 15. This previous bearing wall 15 usually runs parallel to thediffuser wall 11.

Thus looking at the FIGURE it is evident that the first section 13 ofthe bearing housing wall 12 formed obliquely according to the inventionruns significantly inclined to the radial direction 14, as a result ofwhich in particular the risk of a flow separation and of an undesirableback flow in the diffuser 7 near the bearing housing wall 12 at lowcircumferential speeds and thus also low mass flows, i.e. in the rangeof a surge limit, can be substantially reduced, as a result of which inthis operating range a significantly increased efficiency can beachieved.

A width a on the diffuser outlet 9 corresponds to approximately 0.375B≦a≦0.95 B of the width B on the diffuser inlet 8. Looking at the FIGUREit is evident that the width B corresponds to the sum of b and c,wherein b corresponds to a diffuser width of a compressor known from theprior art.

In addition to this, a ratio of a diffuser width a to b amounts toapproximately 0.6 to 0.95, wherein a corresponds to a diffuser width ofthe charging device 1 according to the invention, while b marks thediffuser width of a diffuser known from the prior art.

At the same time it is evident that an axial shift of the bearinghousing wall 12 in the region of the diffuser inlet 8 compared with abearing housing wall 15 of a charging device known from the prior arttakes place, namely by a value c between 0.2 mm and 1 mm.

According to the FIGURE it is additionally evident that the compressorwheel 6 engages with a wheel back 16 into a recess 17 on the bearinghousing 4.

The first section 13 radially on the outside is adjoined by a radiallyextending second section 18 of the bearing housing wall 12, which opensinto a volute 19 of the compressor housing 10. The second section 16 inthis case runs preferentially parallel to the diffuser wall 11. A radiallength L₂ of the second section 18 amounts to approximately 100% to 250%of the radial length L₁ of the first section 13. The length L₂ followsthe length L₁ and goes as far as to the outer diameter of the diffuser 7or of the compressor 3.

In addition it can be provided that the first section 13 is formed inone piece with the bearing housing wall 12 or that the first section 13and the second section 18 of the bearing housing wall 12 are formed as aseparate insert and connected to the bearing housing wall 12. The firstcase offers the great advantage that a comparatively cost-efficientproduction is made possible since the first section 13 and the secondsection 18 can be produced in one piece and thus in a common productionstep with the bearing housing 4. With the second mentioned embodimentthere is the advantage that the first and second section 13, 18 formedas a separate insert makes possible a flexible assembly as a result ofwhich the bearing housing previously used could be continued to be used.The previous bearing housing wall 15, which is shown drawn with dashedline, constitutes an outer limit of the bearing housing produced up tonow.

In the region of the diffuser 7, the bearing housing wall 12 cancomprise a cooling duct or an air gap insulation. The charging device 1according to the invention can be employed for example in an internalcombustion engine 20.

With the charging device 1 according to the invention, in particular asignificantly increased efficiency in the lower rotational speed range,i.e. near a surge limit, can be achieved since a flow separation or aback flow in the diffuser 7 can be reduced here.

1. A charging device comprising: a compressor; a bearing housing; shaftthat is rotatably mounted in the bearing housing; a compressor wheelarranged on the shaft; and diffuser, which radially extends from adiffuser inlet on the compressor wheel towards a diffuser outlet on aspiral-shaped compressor housing; wherein the diffuser is delimited by adiffuser wall and a bearing housing wall; and wherein a first section ofthe bearing housing wall is oriented originating from the diffuser inletby an angle ranging from 2° to 30° obliquely to a radial direction andbrings about a tapering of the diffuser cross section in the radialdirection away from the shaft.
 2. The charging device according to claim1, wherein a width of the diffuser outlet corresponds to approximately0.375 to 0.95 the times a width of the diffuser inlet.
 3. The chargingdevice according to claim 1, wherein the compressor wheel has a wheelback and engages into a recess on the bearing housing.
 4. The chargingdevice according to claim 1, wherein the charging device is designed asexhaust gas turbocharger.
 5. The charging device according to claim 1,wherein the first section is adjoined by a radially extending secondsection of the bearing housing wall at an end radially away from theshaft, the bearing housing wall opening into a volute of the compressorhousing.
 6. The charging device according to claim 5, wherein a radiallength of the second section corresponds to approximately 100% to 250%of a radial length of the first section.
 7. The charging deviceaccording to claim 1, wherein the first section is formed in one piecewith the bearing housing wall.
 8. The charging device according to claim1, wherein the first section and the second section of the bearinghousing wall are formed as separate inserts and are connected to thebearing housing wall.
 9. The charging device according to claim 1,wherein the bearing housing wall in a region of the diffuser includesone of a cooling duct or an air gap insulation.
 10. An internalcombustion engine comprising a charging device including: a compressor;a bearing housing; a shaft that is rotatably mounted in the bearinghousing; a compressor wheel arranged on the shaft; and a diffuser, whichradially extends from a diffuser inlet on the compressor wheel towards adiffuser outlet on a spiral-shaped compressor housing; wherein thediffuser is delimited by a diffuser wall and a bearing housing wall; andwherein a first section of the bearing housing wall is orientedoriginating from the diffuser inlet by an angle ranging from 2° to 30°obliquely to a radial direction and brings about a tapering of thediffuser cross section in the radial direction away from the shaft. 11.The internal combustion engine according to claim 10, wherein a width ofthe diffuser outlet corresponds to approximately 0.375 to 0.95 times awidth of the diffuser inlet.
 12. The internal combustion engineaccording to claim 10, wherein the compressor wheel has a wheel back andengages into a recess on the bearing housing.
 13. The internalcombustion engine according to claim 10, wherein the charging device isdesigned as an exhaust gas turbocharger.
 14. The internal combustionengine according to claim 10, wherein the first section is adjoined by aradially extending second section of the bearing housing wall at an endradially away from the shaft, the bearing housing wall opening into avolute of the compressor housing.
 15. The internal combustion engineaccording to claim 14, wherein a radial length of the second sectioncorresponds to approximately 100% to 250% of a radial length of thefirst section.
 16. The internal combustion engine according to claim 10,wherein the first section is formed in one piece with the bearinghousing wall.
 17. The internal combustion engine according to claim 10,wherein the first section and the second section of the bearing housingwall are formed as separate inserts and are connected to the bearinghousing wall.
 18. The internal combustion engine according to claim 10,wherein the bearing housing wall in a region of the diffuser includesone of a cooling duct or an air gap insulation.
 19. An exhaust gasturbocharger comprising: a compressor; a bearing housing; a shaft thatis rotatably mounted in the bearing housing; a compressor wheel arrangedon the shaft; and a diffuser, which radially extends from a diffuserinlet on the compressor wheel towards a diffuser outlet on aspiral-shaped compressor housing; wherein the diffuser is delimited by adiffuser wall and a bearing housing wall; wherein a first section of thebearing housing wall is oriented originating from the diffuser inlet byan angle ranging from 2° to 30° obliquely to a radial direction andbrings about a tapering of the diffuser cross section in the radialdirection away from the shaft; and wherein the first section is adjoinedby a radially extending second section of the bearing housing wall at anend radially away from the shaft, the bearing housing wall opening intoa volute of the compressor housing.
 20. The exhaust gas turbochargeraccording to claim 19, wherein a radial length of the second sectioncorresponds to approximately 100% to 250% of a radial length of thefirst section.